"From what I'm hearing on the grape vine is that they’ve given full support to Dasher," one Louisiana Republican operative said of the Robertsons.

State Sen. Neil Riser, whom McAllister defeated in the special election runoff for the seat, also announced on Monday that he will not run for the seat.

"I won’t be running in the 5th Congressional District this fall," Riser told LA Politics on Monday. "I’m not ruling anything else out in the future, but I’m not going to be a part of this race in the fall."

Candidates have until Aug. 22 to file the necessary paperwork to run in Louisiana. In the state, all candidates who qualify run on the same ballot in November. If no candidate garners at least 50 percent of the vote, the race proceeds to a December runoff.

Louisiana's 5th District is heavily Republican territory. GOP presidential nominee Mitt Romney carried the district with 61 percent in 2012.

The race is rated a Safe Republican contest by the Rothenberg Political Report/Roll Call.